import numpy as np
import pandas as pd
arr = np.random.randint(1, 20, size=(3, 3))
df = pd.DataFrame(arr, columns=['a', 'b', 'c'])
print('原始数据: \n', df)
print('每列求和聚合: \n', df.agg('sum'))
print('每列同时求和及平均值聚合: \n', df.agg(['sum', 'mean']))
def rang(arr):
    return arr.max() - arr.min()
print('各行分别求和、平均值和极差聚合:\n',df.agg({0: 'sum',1: 'mean',2: rang}, axis=1))
